In the field of compressing audio-visual (AV) data the technological trend goes towards increasingly parameter-oriented descriptions. Seen from an encoding point of view, compression parameters in general specify, in which of several possible modes certain parts of the encoder input (AV data) shall be processed. Correspondingly, from a decoding point of view, those same compression parameters indicate, according to which of several allowable rules a section of a given compressed bit stream shall be converted back into a piece of AV data. Compression parameters can be of different nature; assuming a compression scheme where pictures are sub-divided into slices, they may be “global parameters (GP)”, “picture layer parameters (PLP)” and “slice layer parameters (SLP)”. It is expected that GP are mostly constant, since they express parameters such as picture size or color space. However, they could be changed at the start of a random access unit, such as a GOP. Therefore, a small set of different GP sets will be referenced from within an AV bit stream. PLPs express parameters that might change more frequently, at a maximum on a per-picture basis. Hence, each coded picture will reference one out of a potentially larger set of such PLPs. Similarly, different SLPs could be referenced by each coded slice within a coded picture. It is expected that GP are mostly predetermined by the nature of the specific AV material being compressed, whereas PLP and SLP can be freely chosen as part of the encoder optimization. For the latter, the selection is likely to be based on some kind of compression efficiency measure quantifying either the coding error or the compression bit rate or both. The above-mentioned technology will be used in the developing MPEG-4 Part 10, also known as H.26L or JVT codec.